This invention pertains to the separation of cobalt from nickel and in particular to a liquid-liquid extraction procedure in which cobalt thiocyanate is extracted into an organic phase and nickel thiocyanate remains in an aqueous phase.
Cobalt and nickel are similar in their chemical and physical properties as would be expected from their relative positions in the periodic table of the elements. It is therefore difficult to effect a practical separation of these two metals which are found together in nature. Their ores have been treated in numerous ways to effect a separation of nickel from cobalt. One such technique involves the conversion of these metals to their respective thiocyanates in an aqueous solution and the extraction therefrom of cobalt thiocyanate by treatment with a water-immiscible organic solvent leaving the nickel thiocyanate in aqueous solution. In one commercial operation nickel and cobalt ores are converted to the corresponding sulfates or carbonates which in turn are treated with thiocyanic acid dissolved in methyl isobutyl ketone (hexone). Alcohols, ketones, and ethers have been broadly disclosed for use as the organic water-immiscible solvent in liquid-liquid extraction processes for separating cobalt from nickel. However all of these disclosures suffer from a drawback, namely, the extraction of the cobalt into the organic phase is not as efficient or clear cut as desired.